From an exposure of 25.5~kiloton-years of the Super-Kamiokande detector, 900
muon-like and 983 electron-like single-ring atmospheric neutrino interactions
were detected with momentum pe​>100 MeV/c, pμ​>200 MeV/c, and
with visible energy less than 1.33 GeV. Using a detailed Monte Carlo
simulation, the ratio (μ/e)DATA​/(μ/e)MC​ was measured to be 0.61±0.03(stat.)±0.05(sys.), consistent with previous results from the
Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from
theoretical models of atmospheric neutrino production.Comment: 14 pages with 5 figure